Bruno Bianco

Computational methods for ultrasonic bone assessment

Ultrasound has been proposed as a means to noninvasively assess bone and, particularly, bone strength and fracture risk. Although there has been some success in this application, there is still much that is unknown regarding the propagation of ultrasound through bone. Because strength and fracture risk are a function of both bone mineral density and architectural structure, this study was carried out to examine how architecture and density interact in ultrasound propagation. Due to the difficulties inherent in obtaining fresh bone specimens and associated architectural and density features, simulation methods were used to explore the interactions of ultrasound with bone. A sample of calcaneal trabecular bone was scanned with micro-CT and subjected to morphological image processing (erosions and dilations) operations to obtain a total of 15 three-dimensional (3-D) data sets. Fifteen two-dimensional (2-D) slices obtained from the 3-D data sets were then analyzed to evaluate their respective architectures and densities. The architecture was characterized through the fabric feature, and the density was represented in terms of the bone volume fraction. Computer simulations of ultrasonic propagation through each of the 15 2-D bone slices were carried out, and the ultrasonic velocity and mean frequency of the received waveforms were evaluated. Results demonstrate that ultrasound propagation is affected by both density and architecture, although there was not a simple linear correlation between the relative degree of structural anisotropy with the ultrasound measurements. This study elucidates further aspects of propagation of ultrasound through bone, and demonstrates as well as the power of computational methods for ultrasound research in general and tissue and bone characterization in particular.

Computer-generated holograms of tilted planes by a spatial frequency approach

Computer-generated holograms of plane surfaces tilted and shifted with respect to the hologram plane are considered. The analysis is made in the spatial frequency domain by using the translation and rotation transformations of angular spectra. The frequency approach permits the use of the fast-Fourier-transform algorithm, which decreases the computation time and makes it possible to consider any position of the planes in space. Various configurations of tilted and shifted planes have been investigated, and computer-generated holograms of off-axis planes have been obtained. Computer and optical reconstructions, both of which show the feasibility of the proposed approach, have been carried out.

From the Langevin-Lorentz to the Zeeman model of electromagnetic effects on ligand-receptor binding

Abstract This paper attempts to elucidate the mechanism of action of electromagnetic exposure on ligand-receptor binding. The classical Langevin-Lorentz model, which can be used to describe the adsorption process of a messenger ion, is reviewed and discussed. We conclude that low intensity exposure does not affect appreciably the ion dynamics in the presence of background thermal white noise. A more realistic evaluation of the endogenous field present in a binding site leads to a quantum model based on weak Zeeman-Stark effects. The case of the Zeeman effect is studied in detail assuming a three-state binding site. The density operator method is used, introducing suitable lifetimes which model the thermal bath interaction. The closed form expression for the binding probability is found, as a function of the ligand-receptor parameters and of the electromagnetic sinusoidal exposure.

Frequency analysis of light diffraction between rotated planes

The relation for the angular spectra of rotated planes is evaluated, starting from the knowledge of the mono-chromatic scalar field on a given plane. Diffracted light on a tilted plane can then be calculated in the frequency domain by fast-Fourier-transform algorithms. Unlike the Fresnel and Fraunhofer approaches, this analysis does not require approximations; as a consequence, it permits any positions in space for the planes under investigation. Digital images are generated, which show the effects of rotation.

Launcher and microstrip characterization

A method for identifying scattering parameters of launchers and uniform microstrips is presented. It is shown that 8 complex measurements (magnitude and phase) on two microstrips which are different only in length, inserted between two launchers, can give, with suitable algebraic treatment, the S-parameters of either the microstrips and the launchers. This technique is promising for deembedding active devices as well for microstrip discontinuities.

The Role of the Magnetic Field in the EM Interaction with Ligand Binding

Low-intensity magnetic induction fields (<(10 mT) can affect bioelectrochemical processes directly through the magnetic component of the Lorentz force, provided that some specific conditions are fulfilled1. This conclusion has been drawn after that an international consensus about the need for re-evaluating the role played by the magnetic fields was reached during the NATO Advanced Research Workshop “Interactions Between Electromagnetic Fields and Cells”, held at the E. Majorana Centre for Scientific Culture at Erice (Italy) in September 1984. Notwhitstanding the leading action of A.R. Liboff, his suggestion to study the motion of a charged particle (ion) in a constant magnetic field inside a helical membrane channel2 remains rather qualitative and has not yet reached the maturity of a mathematical model. The attempt to offer some quantitative basis for Liboff’s ideas turned out to be a failure3, as the related paper contains several theoretical pitfalls.

Sinusoidal ELF magnetic fields affect acetylcholinesterase activity in cerebellum synaptosomal membranes.

The effects of extremely low frequency magnetic fields (ELF-MF) on acetylcholinesterase (AChE) activity of synaptosomal membranes were investigated. Sinusoidal fields with 50 Hz frequency and different amplitudes caused AChE activity to decrease about 27% with a threshold of about 0.74 mT. The decrease in enzymatic activity was independent of the time of permanence in the field and was completely reversible. Identical results were obtained with exposure to static MF of the same amplitudes. Moreover, the inhibitory effects on enzymatic activity are spread over frequency windows with different maximal values at 60, 200, 350, and 475 Hz. When synaptosomal membranes were solubilized with Triton, ELF-MF did not affect AChE activity, suggesting the crucial role of the membrane, as well as the lipid linkage of the enzyme, in determining the conditions for inactivation. The results are discussed in order to give an interpretation at molecular level of the macroscopic effects produced by ELF-MF on biological systems, in particular the alterations of embryo development in many organisms due to acetylcholine accumulation.

Effect of lifetimes on ligand binding modelled by the density operator

Abstract This paper addresses the problem of evaluating theoretically the effects of electromagnetic (EM) exposure on biological systems. EM fields can affect the chemical activity of ions while they interact with the membrane receptors of a cell during a binding process. A coulombic three-state Zeeman model for the binding site is proposed, and the ion adsorption under low-frequency magnetic exposure is described by means of the density operator. The system interactions with the thermal bath are accounted for by a suitable set of lifetime parameters. The limits of a first-order perturbation approach, which allows us to find a closed-form expression for the ion-binding probability, are discussed. The biological effectiveness of a Helmholtz coil exposure system is rather small if computed according to the simplifying assumptions of the paper.

Evaluation of Errors in Calibration Procedures for Measurements of Reflection Coefficient

Procedures for the calibration of computer-controlled network analyzers in reflection measurements are studied. The major aim of this paper is to develop an error analysis in order to define a quality factor, for evaluating the performances of a calibration procedure. This is done by using the invariance property of the cross ratio, which easily lets one obtain analytical expressions for the residual errors As an application of this technique, a comparison between two actual calibration procedures has been made using an automatic network analyzer. The experimental results favorably compare with the ones obtained on theoretical basis.

Measurements of Complex Dielectric Constant of Human Sera and Erythrocytes

A method for measuring the complex permittivity of biological liquids at microwave frequencies is presented. The calibration needs three reference materials; this method allows measurements to be made very quickly, using only very small amounts of material. Measurements were made on human erythrocytes, obtaining their inner conductivity using Frickes equation, and on human sera of normal and sick individuals. Using an optimization technique, some parameters related to the water bound to the serum proteins were identified, showing differences possibly related to the presence of certain diseases.